4. Acquisition

Time requirement: 9h Sample: commercial 1.4 M n-butyllithium in hexane; add 10% dry [Dg]THF for lock- ing purposes. Seal the sample with parafilm. The measurement can be done at room temperature.

Since the 7H and ⁷Li NMR frequencies are very close, remove any lock stop filter from the transmitter channel at the preamplifier and tune the probe-head for SLi. Record normal ¹H and ⁷Li NMR spectra, change to the 2D mode of the spectrometer, and load the HOESY pulse program. You have to set:

td2: 512 data points in F> tdl: 128 data points in F, sw2: 4 ppm swl: 9 ppm o1: middle of “Li NMR spectrum o2: middle of ¹H NMR spectrum p1, p2: 90° ¹H decoupler pulse p3: 180° ⁷Li transmitter pulse p4: 90° ⁷Li transmitter pulse dl:6s d2: 1.7 s mixing time initial value for ¢, evolution: 3 ys increment for ¢, evolution = 1/[4-sw1] decoupler attenuation and 90° pulse for CPD

5. Processing

Apply zero-filling in F, to 256 real data points. Use exponential windows in both d1- mensions. Apply real Fourier transformation corresponding to the TPP! mode of data acquisition in F,. Phase correction is usually only necessary in F2.

6. Result

The figure shows the result obtained on an AMX-500 spectrometer with a 5 mm mul- tinuclear probe-head. The cross-peaks with the a- and B-protons of butyllithium are clearly visible. The resonance of the B-protons is hidden under one of the resonances of hexane.

7. Comments

The HOESY sequence can be understood from the simple vector analysis. The first pulse creates proton magnetization –/4,. This develops proton chemical shift during f.